Bridge rectifier temperature

[stevene]

I have a 2W10 bridge rectifier and according to a thermal camera, it is operating at >105 deg C (out of range). I would like to know, is this normal? Assuming it is operating at its rated current, it should dissipate about 1.2*2=2.4W (I believe).
Its max operating temperature is also given as 125 deg C, is this assuming normal load conditions?
The temperature seems fairly high to me, bearing in mind there is no heatsink.
Sorry if this question seems uninformed.
Thanks in advance

 

[audioguru]

It won't last long if you operate it near its max allowed temperature.
Then when it fails it might cause a fire or wipe out other parts.

 

[stevene]

It won't last long if you operate it near its max allowed temperature.
Then when it fails it might cause a fire or wipe out other parts.

The overtemp element was one of my initial suspicions. This is work based (hence access to a thermal imager) and I am the only person in the department with ANY qualifications in electronics-albeit a bad one. It is an intermittant recurring fault where a unit shuts itself down, and restarts the PLC process. Seems odd to me for a unit to be operating at a potentially dangerous temperature.

 

[Nigel Goodwin]

I would suggest measuring the current it's passing?, in case the load is drawing too much. It's also possible that one diode might be short, although I would expect that to take out a fuse? - but if it didn't, it would get excessively hot.

You might try the 'wet finger test' - lick your finger tip and touch the rectifier with it (obviously being careful about any electrical contact) - if it goes 'hisssss' as the saliva evaporates, it's really running too hot

Who needs thermal imagers?.

 

[Hero999]

Assuming it's operating off <25VAC otherwise I wouldn't recommend touching it, especially with a wet finger!

 

[Diver300]

The overtemp element was one of my initial suspicions. This is work based (hence access to a thermal imager) and I am the only person in the department with ANY qualifications in electronics-albeit a bad one. It is an intermittant recurring fault where a unit shuts itself down, and restarts the PLC process. Seems odd to me for a unit to be operating at a potentially dangerous temperature.

I woudn't have thought that a rectifier would shut itself down if too hot. It would just go bang.

There may be an overload, which is causing the rectifier to run hot, but some other device overheats and trips a thermal shutdown.

 

[Nigel Goodwin]

Assuming it's operating off <25VAC otherwise I wouldn't recommend touching it, especially with a wet finger!

Which was why I said "(obviously being careful about any electrical contact)", doing so on 230V mains is perfectly normal - but obviously for people who know what they are doing!.